IMPROVED WIRE ROPE ENDURANCE LIFE WITH NYLON SHEAVES.

The endurance life of a 3/4 in. diameter wire rope was tested using nylon and steel sheaves on a simulated lifting device at design factors of 3. 5, 5 and 10 employing sheave ratios of 18/1 and 24/1. The nylon sheaves imparted a distinctively longer endurance life of 1. 33 to 4. 5 times to the wire rope compared with steel sheaves depending on load level and sheave ratio employed. After retiring a total of seven ropes from both the nylon and steel sides, the nylon and steel sheaves were still in operational condition. The substantially longer endurance life of wire rope against nylon sheaves, as comapred to steel sheaves, can be attributed to the unique properties of nylon including resiliency and elasticity. A linear relationship of remaining strength vs. an introduced fatigue factor was found.